This research will make detailed investigations of the human electroretinogram and the visually evoked cortical potential using stimulus alternation. An advantage of alternation is that it produces results that are uncomplicated by stray light. Quantitative studies are to be made of recordings that are produced by stimulation of peripheral regions of the retina. The recording conditions and subsequent analyses will permit a comparison of the results with data from psychophysics and other areas of visual science. Two methods of alternation are to be used. In one method, alternation is produced by an interchange of the elements of the stimulus pattern within the stimulator. Alternation in the second method is produced by the displacement of the retinal image that accompanies saccadic eye movements. Results obtained by the two methods will be compared. A variety of experiments is planned. They will deal with changes in sensitivity as a function of the spatial frequency of the stimulus, of the focus of the image on the peripheral retina, of the locus of the stimulus, of the area of the stimulus, of stimulus rate, and of the pulse-cycle relation. The techniques will permit study of potentials that precede saccadic eye movements and study of the relations between visual potentials and the alpha rhythm. These two topics will also be investigated.